The present invention relates to laminated microchannel devices, static mixing units, and methods of making same.
The desires to reduce costs and increase efficiency have been important factors in promoting advances in modern technology. One technique to reduce the costs of devices is to produce the devices automatically and in large quantities. This technique, known as mass production, was a key to making the automobile widely available. Another common technique to reduce costs is to minaturize devices. A well known example of minaturization is in the computer industry, where computers that formerly occupied entire rooms can now be made the size of a wristwatch. Minaturization saves both space and materials.
Furthermore, the reduction of size, in theory, can increase the efficiency of processes such as heat transfer. Scientists and engineers at Pacific Northwest National Laboratory have been at the forefront of efforts to minaturize fluid-containing systems. The success of these efforts can be seen in the microcomponent systems described by Wegeng et al. in U.S. Pat. Nos. 5,611,214 and 5,811,062. These patents describe microcomponent sheet architecture that can be used in a wide variety of devices including heat exchangers, fuel processing units, chemical separators, and chemical processing.
Other minaturized chemical reactors, sometimes called xe2x80x9creactor-on-a-chip technologyxe2x80x9d, are formed on a single layer, usually silicon. An example of a multilayer chemical reactor is described by Ashmead et al. in U.S. Pat. No. 5,534,328. In column 3 of the patent, Ashmead et al. suggest various materials and state that the laminae can be processed by selected subtractive, additive, and forming processes. At column 6, lines 55-60, Ashmead et al. state that their invention preferably uses materials of groups III, IV, and V of the Periodic Table, most preferably silicon and germanium. In the xe2x80x9cMethod Of Fabricationxe2x80x9d section of the patent, the desposition and etching of silicon and silicon compounds is described.
Methods for forming complex microstructures in silicon are well-known and have found applicability in making microfluidic devices. It would be desirable to form microfluidic devices from plastic. Plastic is cheap, light-weight, durable, and resistant to many chemicals. However, unlike silicon, methods for creating complex microstructures in plastic are not well-established, nor are these methods necessarily amenable to low cost, mass production. Becker et al. in xe2x80x9cMicrofluidic devices for xcexc-TAS applications fabricated by polymer hot embossing,xe2x80x9d describe methods of hot embossing polymer substrates using a heated master material. Becker et al. state that, when silicon was used as the master material, their technique required very tight control over the deembossing process because very small shear stresses could break the fine silicon structures. Becker et al. also state that embossing vertical walls requires high quality embossing tools since any surface defect in the tool is replicated in polymer and that the tool remains in contact with the structured surface during deembossing and slight deformations on the channel edge can be observed due to the frictional forces.
Despite prior efforts at miniturizing microfluidic devices, there remains a need for microchannel devices that can be made by new, inexpensive methods of mass production. There is also a need for multilayer, plastic microchannel devices. There is a corresponding need for new methods of making microchannel devices, especially methods for making plastic and/or multilayer devices.
The present invention provides a laminated microchannel device containing at least a unit operation process layer, and first and second channel containment layers. The unit operation process layer has an inlet and a channel that extends longitudinally through the process layer. The channel is cut through the entire layer, including top and bottom surfaces. One of the channel containment layers forms the top and bottom cover layer. Fluid communication into the inlet and out of the outlet is provided via fluid passages through either or both of the channel containment layers. The surface area of the channel""s inlets and outlets preferably make up less than about 20%, and more preferably less than 10% of the channel""s total surface area.
The invention also provides a method of making a laminated microchannel device in which the channel containment layers and the unit operation process layer are stacked together in a laminated device.
In another aspect of the invention, a static mixing unit is provided. The mixing unit has an inlet adapted to convey a first fluid into a central channel. The central channel has sides and an outlet. The mixing unit also has an outer channel having a second inlet adapted to convey a second fluid into the outer channel. The outer channel is disposed around the central channel and at least two connecting channels extend between the outer channel and the central channel and thus provide fluid communication between the outer and central channel. The mixing unit is especially well adapted for insertion in a laminated microchannel device.
The inventive microchannel device and methods provide numerous advantages over the prior art. These advantages include simplicity, rapid construction, and excellent suitability to low cost mass production. The static mixing unit provides intimate mixing of fluid streams without the presence of moving parts. The mixing unit is especially well suited for inclusion in a laminated microchannel device where this novel design provides efficient fluid transport and essentially instantaneous mixing of multiple fluid streams; thus providing an intimately mixed product stream to a subsequent unit process operation layer.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following drawings and description.
xe2x80x9cUnit operation process layerxe2x80x9d means that an entire process, such as mixing, is conducted within a single layer, i.e., the unit process does not extend through several layers of a laminated device.
xe2x80x9cLaminaxe2x80x9d means a single sheet of material.
xe2x80x9cLayerxe2x80x9d can include a lamina, adhesive layers and parts of upper and lower laminae.
Elements that are in xe2x80x9cfluid communicationxe2x80x9d means that fluid can flow between the elements. In preferred embodiments, an outlet of one element is directly adjacent the inlet of another element.
A xe2x80x9cchannelxe2x80x9d in the microchannel device refers to a channel having a length at least five times greater than the width, and where the channel width is less than 20% of the sheet width.
A xe2x80x9cchannel containment layerxe2x80x9d is defined in combination with a unit process operation layer, and the channel containment layer blocks at least a portion of the through-cut channel in the unit process operation layer. For example, the channel containment layer can be a cover layer or a second process layer whose channel or channels only overlap with the first unit process operation layer at the inlet and/or outlet.
A xe2x80x9cfluid passagexe2x80x9d is a through hole, channel or other passage that allows fluid flow therethrough.
A xe2x80x9cmicrogroovexe2x80x9d is a groove (on the micrometer scale) that is cut only part way through a layer.